Heat-sensitive recording medium

Abstract

Disclosed is a heat-sensitive recording material having a heat-sensitive recording layer containing a leuco dye, a developer, and an adhesive on a support body, in which the heat-sensitive recording material is characterized by containing an olefin-acrylic copolymer salt and a styrene-butadiene latex as the adhesive, and in which the amount of the olefin-acrylic copolymer salt is less than the amount of the styrene-butadiene latex. The present invention relates to a liquid crystal composition comprising a liquid crystal compound selected from the group consisting of a compound represented by general formula (1) (in formula (1): R each represents a C1-12 alkyl group, a C7-12 aralkyl group, or a C6-12 aryl group, the aralkyl group and the aryl group may be substituted by a C1-12 alkyl group, a C1-12 alkoxy group, a C6-12 aryl group, or a halogen atom, and a plurality of R may be the same or different; and each A1 represents a hydrogen atom or a C1-4 alkyl group, and a plurality of A1 may be the same or different. ) is represented by formula (1). The N, N '-diarylurea compound is represented by general formula (2) (in formula (2), R1 to R5 may be the same as or different from each other; compounds represented by general formula (3) and each represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group. And at least one non-phenolic color-developing agent selected from the group consisting of the compounds represented by the formula (1) is used as a color-developing agent. # imgabs0 # # imgabs1 # # imgabs2 #

Description

Technical Field

[0001] The present invention relates to a thermosensitive recording body. Background Art

[0002] Generally, a thermosensitive recording body that generates a recorded image on at least one surface of a support made of paper, synthetic paper, synthetic resin film, etc. by applying heat energy to cause a color-developing reaction between a leuco dye and a developer has the following advantages: For example, the recording devices for these are compact and inexpensive, and are easy to maintain. Such thermosensitive recording bodies are widely used as recording media for facsimile machines, ticket vending machines, and scientific measuring instruments, and as output media for various printers and plotters for POS labels, CAD, CRT medical images, etc. In particular, those including synthetic paper or synthetic resin film as a support exhibit excellent water resistance and excellent image quality, and thus the usage amount as an output medium for various printers for food labels, medical labels, medical images, etc. has shown a significant increase.

[0003] However, different from a paper-based support, a film-based support such as synthetic paper does not absorb the coating material constituting the layer formed on the support, and the adhesiveness between the base material and the thermosensitive recording layer, and between the thermosensitive recording layer and the protective layer is more likely to decrease compared with a support made of paper. Such insufficient adhesiveness causes peeling, particularly peeling from the base material due to elution of water-soluble components when wetted with water; in addition, peeling can easily occur when an external mechanical force is applied. This causes peeling of the printed recording portion, resulting in problems such as defects in barcode reading.

[0004] In order to improve the adhesiveness between a synthetic paper base material and a thermosensitive recording layer, Patent Document 1 and Patent Document 2 propose a thermosensitive recording body including a thermosensitive recording layer containing a styrene-butadiene copolymer. Although this thermosensitive recording body achieves excellent adhesiveness, when it is immersed in water, the coating film peels off; therefore, further improvement is required.

[0005] Prior art documents

[0006] Patent documents

[0007] Patent Document 1: JPH08-175007A

[0008] Patent Document 2: JPH09-226246A Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] The main object of the present invention is to provide a thermosensitive recording medium that has no risk of transferring printed content onto the printing surface and has excellent thermal background fogging resistance.

[0011] Means for Solving the Problem

[0012] To achieve the above object, the present inventors conducted extensive research and found that the above object can be achieved by providing a thermosensitive recording medium comprising a thermosensitive recording layer on a support, the thermosensitive recording layer containing a leuco dye, a developer, and a binder, the thermosensitive recording layer containing an olefin-acrylic copolymer salt and a styrene-butadiene latex as the binder, and containing a specific non-phenolic developer as the developer. Thus, the present invention was completed. That is, the present invention relates to the following thermosensitive recording medium.

[0013] Item 1: A thermosensitive recording medium comprising a thermosensitive recording layer on a support,

[0014] the thermosensitive recording layer containing a leuco dye, a developer, and a binder,

[0015] the thermosensitive recording layer containing an olefin-acrylic copolymer salt and a styrene-butadiene latex as the binder, and containing at least one non-phenolic developer selected from the group consisting of N,N'-diarylurea compounds represented by the following formula (1), compounds represented by the following formula (2), and compounds represented by the following formula (3) as the developer:

[0016]

[0017] wherein

[0018] R represents C 1-12 alkyl, C 7-12 aralkyl, or C 6-12 aryl, the aralkyl and aryl may be substituted with C 1-12 alkyl, C 1-12 alkoxy, C 6-12 aryl, or a halogen atom, and a plurality of Rs may be the same or different, and

[0019] A 1 represents a hydrogen atom or C 1-4 alkyl, and a plurality of As 1 may be the same or different;

[0020]

[0021] wherein

[0022] R 1 to R 5identical or different, and each represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group;

[0023] .

[0024] Item 2: The heat-sensitive recording medium according to Item 1, wherein the N,N'-diarylurea compound represented by the formula (1) is at least one selected from the group consisting of: N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(4-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea and N,N'-di-[2-(p-toluenesulfonyloxy)]phenylurea.

[0025] Item 3: The heat-sensitive recording medium according to Item 1 or 2, wherein the N,N'-diarylurea compound represented by the formula (1) is N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

[0026] Item 4: The heat-sensitive recording medium according to any one of Items 1 to 3, wherein the compound represented by the formula (2) is 3-[(phenylcarbamoyl)amino]phenyl 4-methylbenzenesulfonate.

[0027] Item 5: The heat-sensitive recording medium according to any one of Items 1 to 4, wherein based on the total solid content of the heat-sensitive recording layer, the content of the olefin-acrylic copolymer salt is 4 to 25% by mass, and the content of the styrene-butadiene latex is 15 to 40% by mass.

[0028] Item 6: The heat-sensitive recording medium according to any one of Items 1 to 5, wherein the content of the olefin-acrylic copolymer salt is 10 to 150 parts by mass relative to 100 parts by mass of the styrene-butadiene latex.

[0029] Item 7: The thermosensitive recording layer according to any one of Items 1 to 6, wherein the total content of the olefin-acrylic copolymer salt and the styrene-butadiene latex is 25 to 50% by mass based on the total solid content of the thermosensitive recording layer.

[0030] Item 8: The thermosensitive recording body according to any one of Items 1 to 7, wherein the support is synthetic paper or a synthetic resin film.

[0031] Item 9: The thermosensitive recording body according to any one of Items 1 to 8, wherein the support contains a polyolefin resin.

[0032] Item 10: The thermosensitive recording body according to any one of Items 1 to 9, which includes a protective layer on the thermosensitive recording layer, and the protective layer contains acetoacetylated polyvinyl alcohol as a binder.

[0033] Effects of the Invention

[0034] The thermosensitive recording body of the present invention has no risk of transferring the printed content to the printing surface and has excellent heat-resistant background fogging property. Detailed Description of the Invention

[0035] In this specification, the expressions "comprise" or "contain" include the concepts of "comprising", "consisting essentially of", and "consisting of".

[0036] In this specification, the numerical range represented by "… to (~) …" means a range including the values given before and after "to (~)" as the lower limit value and the upper limit value.

[0037] As used herein, "latex" includes latex in the form of a gel or a dry film formed by drying the dispersion medium.

[0038] Support

[0039] The type, shape, size, etc. of the support used in the present invention are not particularly limited, and can be appropriately selected from, for example, high-quality paper (acidic paper, neutral paper), medium-quality paper, coated paper, art paper, cast-coated paper, cellophane, resin laminated paper, polyolefin synthetic paper, synthetic fiber paper, non-woven fabric, synthetic resin film, and various transparent supports. The thickness of the support is not particularly limited and is usually about 20 to 200 μm.

[0040] The support of the present invention is preferably synthetic paper or a synthetic resin film. The synthetic paper or synthetic resin film used as the support in the present invention is not particularly limited, and the base material may be, for example, a polyolefin film such as polyethylene or polypropylene; a polystyrene film; a polyester film such as polyethylene terephthalate or polybutylene terephthalate; or a cellulose derivative film such as cellulose triacetate. The support may contain pigments. For example, synthetic paper produced by a method including the following can be used: kneading a polyolefin resin and a white inorganic pigment while heating; extruding the kneaded product from a die; stretching the extruded product in the longitudinal direction; forming one or two layers of a film containing a polyolefin resin and a white inorganic pigment on each side of the stretched product; and stretching the obtained product in the transverse direction to make it translucent or opaque. Since the synthetic paper contains a polyolefin resin, the adhesiveness to the thermal recording layer is still poor; however, due to the formation of voids by the pigments, both cushioning properties and heat insulating properties are achieved, and excellent color development properties and excellent image quality are achieved. Although using synthetic paper as the support can produce an anchoring effect on the thermal recording layer, the water resistance is reduced due to the presence of water permeating into the voids; therefore, the use of synthetic paper as the support is limited. However, according to the present invention, synthetic paper can fully exhibit its effects and can be preferably used.

[0041] Thermosensitive recording layer

[0042] The thermal recording layer in the present invention contains an olefin-acrylic copolymer salt and a styrene-butadiene latex as binders and is formed on a support. Therefore, excellent water resistance, water barrier properties, and adhesiveness between the support and the thermal recording layer can be obtained. In addition to the water barrier properties, a synergistic effect with a specific non-phenolic developer (described later) is obtained, and the risk of transferring the printed content to the printing surface is eliminated.

[0043] The olefin-acrylic copolymer salt used in the present invention can exhibit high water resistance because the olefin part has high hydrophobicity. In addition, the carboxyl part of the olefin-acrylic copolymer salt has excellent adhesiveness to the film and can exhibit high adhesiveness.

[0044] Examples of the olefin component in the olefin-acrylic copolymer salt include ethylene, propylene, butene, and isobutene, etc. Among them, from the viewpoints of water resistance and adhesiveness, an ethylene-acrylic copolymer resin is preferably used. The proportion of the olefin component in the olefin-acrylic copolymer salt is preferably about 50 to 90 mol%.

[0045] The weight-average molecular weight of the olefin-acrylic copolymer salt is preferably from 20,000 to 200,000, and more preferably from 30,000 to 150,000. Setting the molecular weight to 20,000 or more can improve water resistance and adhesiveness. Setting the molecular weight to 200,000 or less enables excellent film-forming property and can improve adhesiveness. The weight-average molecular weight is measured by gel permeation chromatography using polystyrene as a standard sample.

[0046] Examples of the salt of the olefin-acrylic copolymer salt include salts with alkali metals such as lithium, potassium, and sodium, and ammonium salts, etc. Among them, ammonium salts are preferred from the viewpoint of improving water dispersibility and water resistance.

[0047] The content of the olefin-acrylic copolymer salt is preferably from 4 to 25% by mass, more preferably from 5 to 20% by mass, and even more preferably from 5 to 15% by mass based on the total solid content of the thermosensitive recording layer. Setting the content to 4% by mass or more can improve water resistance. Setting the content to 25% by mass or less can improve color developability.

[0048] The olefin-acrylic copolymer salt can be commercially obtained, for example, as Chemipearl S100, S650, S75N, etc. produced by Mitsui Chemicals, Inc. and Hi-Tec S3121, S8512, etc. produced by Toho Chemical Industry Co., Ltd., and can be easily obtained and used in the form of an emulsion.

[0049] The styrene-butadiene latex used in the present invention is preferably a latex having a butadiene monomer content of 20 to 45% by mass based on the solid content of all monomers and a gel content of 70 to 85%. Setting the copolymerization ratio of butadiene to 20% by mass or more can improve film-forming property. Setting the content to 45% by mass or less can increase cohesion and improve pick-up strength. In addition, setting the gel content to 70% or more can improve adhesion strength. From the viewpoint of improving the stability of the latex, the content of the styrene monomer constituting the styrene-butadiene latex is preferably about 40 to 70% by mass.

[0050] The styrene-butadiene latex used in the present invention contains styrene and butadiene as main constituent monomers, and for the purpose of modification, at least one selected from various unsaturated carboxylic acid monomers may be further contained in the monomer composition. Specific examples of such unsaturated carboxylic acid monomers include itaconic acid, maleic acid, acrylic acid, methacrylic acid, fumaric acid, dicarboxylic anhydrides, and monoalkyl dicarboxylates, etc. It is desired that these monomers be contained in the monomer composition in an amount of 0.5 to 10% by mass. The monomer composition of the styrene-butadiene latex may further contain other monomers. Specific examples of such other monomers include aromatic vinyl monomers such as α-methylstyrene, vinyltoluene, and dimethylstyrene; acrylate monomers such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate; methacrylate monomers such as methyl methacrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate; and glycidyl group-containing monomers such as glycidyl acrylate and glycidyl methacrylate; etc. These monomers may be used in an amount of about 0 to 35% by mass as long as they do not impair the effects of the present invention.

[0051] The production method of the styrene-butadiene latex is not particularly limited. For example, known emulsion polymerization methods such as continuous emulsion polymerization and batch emulsion polymerization can be used. At this time, various known additives for ordinary emulsion polymerization such as emulsifiers, chain transfer agents, polymerization initiators, electrolytes, and chelating agents can be appropriately used. In addition, the polymerization temperature can be selected as high temperature or low temperature.

[0052] The content of the styrene-butadiene latex is preferably 15 to 40% by mass, and more preferably 15 to 30% by mass, based on the total solid content of the thermosensitive recording layer. Setting the content to 15% by mass or more can improve the adhesiveness. Setting the content to 40% by mass or less can improve the color development property.

[0053] The total content of the olefin-acrylic copolymer salt and the styrene-butadiene latex is preferably 25 to 50% by mass, more preferably 25 to 40% by mass, and even more preferably 25 to 30% by mass, based on the total solid content of the thermosensitive recording layer. Setting the total content to 25% by mass or more can improve the water resistance, water barrier property, and adhesiveness. Setting the total content to 50% by mass or less can improve the color development property.

[0054] In the thermosensitive recording layer, the content of the olefin-acrylic copolymer salt is preferably 10 to 150 parts by mass, more preferably 20 to 100 parts by mass, and even more preferably 30 to 90 parts by mass relative to 100 parts by mass of the styrene-butadiene latex. Setting the content of the olefin-acrylic copolymer salt to 10 parts by mass or more can improve water resistance and water barrier properties. Setting the content to 150 parts by mass or less can improve color developability and can produce a synergistic effect in terms of adhesiveness.

[0055] The binder used for the thermosensitive recording layer in the present invention is an olefin-acrylic copolymer salt and a styrene-butadiene latex. However, as long as the effects of the present invention are not impaired, various other known binders can also be used as needed. Examples of other binders include water-soluble binders such as starches, such as oxidized starch, acid-modified starch, phosphorylated starch, enzyme-modified starch, cation-modified starch, esterified starch, etherified starch, and vinyl acetate-modified grafted starch; cellulose derivatives such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose, methoxy cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose; polyvinyl alcohols such as fully (or partially) saponified polyvinyl alcohol, silicon-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, and acetoacetyl-modified polyvinyl alcohol; and sodium polyacrylate, polyacrylamide, polyvinyl pyrrolidone, acrylamide-acrylate copolymer, acrylamide-acrylate-methacrylic acid copolymer, basic salt of styrene-maleic anhydride copolymer, basic salt of isobutene-maleic anhydride copolymer, sodium alginate, gelatin, and casein; and water-dispersible binders of latexes such as polyvinyl acetate, polyurethane, polyacrylic acid, polyacrylate, polybutyl methacrylate, vinyl chloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, and styrene-butadiene-acrylic copolymer.

[0056] In the present invention, the leuco dyes contained in the thermosensitive recording layer can be selected from various known leuco dyes. For example, the leuco dyes used can be at least one black-developing leuco dye selected from the following: 3-diethylamino-6-methyl-7-anilinofluoran, 3-di(n-butyl)amino-6-methyl-7-anilinofluoran, 3-di(n-pentyl)amino-6-methyl-7-anilinofluoran, 3-(N-ethyl-N-isopentylamino)-6-methyl-7-anilinofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-anilinofluoran, 3-pyrrolidino-6-methyl-7-anilinofluoran, 3-diethylamino-7-(m-trifluoromethylanilino)fluoran, 3-(N-isopentyl-N-ethylamino)-7-(o-chloroanilino)fluoran, 3-(N-ethyl-N-2-tetrahydrofurfurylamino)-6-methyl-7-anilinofluoran, 3-diethylamino-6-chloro-7-anilinofluoran, 3-(N-n-hexyl-N-ethylamino)-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-ethylamino]-6-methyl-7-anilinofluoran, 3-[N-(3-ethoxypropyl)-N-methylamino]-6-methyl-7-anilinofluoran, 3-diethylamino-7-(2-chloroanilino)fluoran, 3-di(n-butyl)amino-7-(2-chloroanilino)fluoran, and the like. Leuco dyes that develop colors other than black, such as red, magenta, orange, blue, and green, can also be used as needed.

[0057] The leuco dyes used in the present invention are not limited to these, and can be a combination of two or more. The content of the leuco dye is preferably about 3 to 30% by mass based on the total solid content of the thermosensitive recording layer.

[0058] In the present invention, when the leuco dye is used in the form of solid fine particles, the leuco dye can be pulverized using water as a dispersion medium with a sand mill, grinder, ball mill, co-ball mill, or other various wet pulverizers. The resulting product can be dispersed with a dispersion medium and a water-soluble synthetic polymer compound such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, sulfone-modified polyvinyl alcohol, other modified polyvinyl alcohols, methylcellulose, carboxymethylcellulose, hydroxypropylmethylcellulose, styrene-maleic anhydride copolymer salt or its derivatives, and optionally together with a surfactant, defoaming agent, etc. to obtain a dispersion. The dispersion thus obtained can be used to prepare a coating liquid for the thermosensitive recording layer.

[0059] Optionally, by dissolving a leuco dye in a solvent, emulsifying and dispersing the resulting solution in water using the above water-soluble polymer as a stabilizer, and then evaporating the solvent from the resulting emulsion, the leuco dye used can be formed into solid fine particles. In any case, in order to obtain the desired color sensitivity, the average particle diameter of the dispersed leuco dye particles used in the form of solid fine particles is preferably 0.2 to 3.0 μm, and more preferably 0.3 to 1.0 μm.

[0060] In the present invention, in addition to the form of the above solid fine particles, the leuco dye can be used as composite particles containing an organic polymer and a leuco dye. Such composite particles can be prepared by known methods. For example, a method for preparing composite particles in which the organic polymer is at least one selected from polyurea and polyurea-polyurethane is described below. Specifically, the composite particles can be prepared by: dissolving a leuco dye and a polymer-forming raw material that forms at least one selected from polyurea and polyurea-polyurethane by polymerization in a water-insoluble organic solvent having a boiling point of 100 °C or lower and mixing them; emulsifying and dispersing the resulting organic solvent solution in a hydrophilic protective colloid solution such as polyvinyl alcohol so that the average particle diameter is about 0.5 to 3 μm; if necessary, further mixing a reactive substance such as polyamine therewith; heating the resulting emulsified dispersion to remove the organic solvent by volatilization; and then polymerizing the polymer-forming raw material. Optionally, the composite particles can be prepared by: dissolving the leuco dye in the polymer-forming raw material; emulsifying and dispersing the resulting solution in the same manner as above so that the average particle diameter is about 0.5 to 3 μm; and then polymerizing the polymer-forming raw material.

[0061] The thermosensitive recording layer in the present invention contains at least one non-phenolic color former selected from the group consisting of the N,N'-diarylurea compounds represented by the above formula (1), the compounds represented by the above formula (2), and the compounds represented by the above formula (3) as a color former. Therefore, there is no risk of transferring the printed content to the printing surface. As used herein, the phenomenon of transferring the printed content to the printing surface refers to the phenomenon described below: Specifically, when two printing surfaces printed with patterns such as a pure black grid pattern or a barcode are wetted with water, the printing sides face each other and overlap, and a blocking test is performed, then dried and peeled from each other, the printed content on each surface is transferred to the other printing surface, or more simply, to the unprinted blank portion on the other printing surface, as a blurred, reversed mirror image. Observation of the printing surface after peeling shows no surface swelling, dissolution, or other changes, and there are also no signs of cohesive failure or delamination of the thermosensitive recording layer or the optionally provided protective layer; therefore, it can be speculated that the color former has undergone some action via moisture. When the support is synthetic paper or a synthetic resin film, moisture does not penetrate to the support side and easily remains on the side opposite to the support, and a significant effect that can be visually discriminated is easily produced. The thermosensitive recording bodies causing this phenomenon are problematic because they impair the quality of the printing material and make it difficult to read the printed information.

[0062] In formula (1), as R, C 1-12 alkyl may be linear, branched, or alicyclic, and is preferably C 1-6 alkyl, and more preferably C 1-3 alkyl. C 1-12 Examples of C 1-12 alkyl include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, cyclopentyl, hexyl, cyclohexyl, 2-ethylhexyl, lauryl, and the like. The alkyl used herein also includes the alkyl moiety of C 1-12 alkoxy.

[0063] Aralkyl means arylalkyl, and C 7-12 Examples of aralkyl include benzyl, 1-phenylethyl, 2-phenylethyl, and 3-phenylpropyl.

[0064] Aryl means a monocyclic or polycyclic group formed by one or more 5- or 6-membered aromatic hydrocarbon rings. C 6-12 Examples of aryl include phenyl, 1-naphthyl, 2-naphthyl, and the like. The aryl used herein also includes the aryl moiety of aralkyl.

[0065] Examples of the halogen atom include fluorine, chlorine, bromine, and iodine.

[0066] In formula (1), the substitution positions of each R-SO3- may be the same or different. The substitution position is preferably the 3-position, 4-position, or 5-position, and more preferably the 3-position. When C represented by R 7-12Aralkyl and C 6-12 When the aryl group is substituted, the number of substituents is not particularly limited and is, for example, 1 to 4.

[0067] The C 1 alkyl group represented by A 1-4 may be linear or branched. Examples include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl.

[0068] The substitution positions of each A 1 may be the same or different. The substitution position is preferably the 3-position, 4-position, or 5-position.

[0069] The N,N'-diarylurea compound represented by the formula (1) is not particularly limited and is preferably at least one selected from the group consisting of: N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(4-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methylphenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea, and N,N'-di-[2-(p-toluenesulfonyloxy)]phenylurea. Among them, N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea is preferred.

[0070] The content of the N,N'-diarylurea compound is not particularly limited and can be adjusted according to the leuco dye used. Generally, the content is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, even more preferably 1 part by mass or more, still more preferably 1.2 part by mass or more, and particularly preferably 1.5 part by mass or more, based on the mass part of the leuco dye. The content of the N,N'-diarylurea compound is also preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less, based on the mass part of the leuco dye. Setting the content to 0.5 part by mass or more can improve the recording performance. Setting the content to 10 parts by mass or less can effectively reduce the background fogging in a high-temperature environment.

[0071] In the above formula (2), by R1 to R 5 The halogen atom represented can be a fluorine atom, a chlorine atom or a bromine atom, among which fluorine atoms and chlorine atoms are preferred.

[0072] The alkyl group can be straight-chain, branched-chain or cyclic, and is preferably a straight-chain or branched-chain alkyl group, and more preferably a straight-chain alkyl group. Generally, the alkyl group is a C 1-12 alkyl group, preferably a C 1-8 alkyl group, more preferably a C 1-6 alkyl group, and even more preferably a C 1-4 alkyl group.

[0073] The alkoxy group can be straight-chain, branched-chain or cyclic, and is preferably a straight-chain or branched-chain alkoxy group, and more preferably a straight-chain alkoxy group. Generally, the alkoxy group is a C 1-12 alkoxy group, preferably a C 2-8 alkoxy group, more preferably a C 2-6 alkoxy group, and even more preferably a C 2-4 alkoxy group.

[0074] The alkylcarbonyloxy group can be straight-chain, branched-chain or cyclic, and is preferably a straight-chain or branched-chain alkylcarbonyloxy group, and more preferably a straight-chain alkylcarbonyloxy group. The alkylcarbonyloxy group is also preferably a C 1-10 alkylcarbonyloxy group.

[0075] The alkylcarbonylamino group can be straight-chain, branched-chain or cyclic, and is preferably a straight-chain or branched-chain alkylcarbonylamino group, and more preferably a straight-chain alkylcarbonylamino group. The alkylcarbonylamino group is also preferably a C 1-10 alkylcarbonylamino group.

[0076] The alkylsulfonylamino group can be straight-chain, branched-chain or cyclic, and is preferably a straight-chain or branched-chain alkylsulfonylamino group, and more preferably a straight-chain alkylsulfonylamino group. The alkylsulfonylamino group is also preferably C 1-10 alkylsulfonylamino group.

[0077] Aryl means a monocyclic or polycyclic group formed by one or more 5- or 6-membered aromatic hydrocarbon rings. Examples of aryl include phenyl, naphthyl and biphenyl.

[0078] The aryloxy group is preferably a C 6-12 aryloxy group. The arylcarbonyloxy group is preferably a C 6-12 arylcarbonyloxy group. The arylcarbonylamino group is preferably a C 6-12 arylcarbonylamino group. The arylsulfonylamino group is preferably a C 6-12 arylsulfonylamino group.

[0079] The monoalkylamino group can be linear, branched or cyclic, and is preferably a linear or branched monoalkylamino group, and more preferably a linear monoalkylamino group. A monoalkylamino group having 1 to 10 carbon atoms in the alkyl group is also preferred.

[0080] The dialkylamino group can be linear, branched or cyclic, and is preferably a linear or branched dialkylamino group, and more preferably a linear dialkylamino group. A dialkylamino group having 1 to 10 carbon atoms in the alkyl group is also preferred.

[0081] The arylamino group can be a monoarylamino group or a diarylamino group, and is preferably a C 6-12 monoarylamino group.

[0082] Specific examples of the compound represented by formula (2) include those in which R 1 to R 5 are each an alkyl group or a hydrogen atom, preferably R 1 to R 5 are each a C 1-8 linear alkyl group or a hydrogen atom, more preferably R 1 to R 5 are each a C 1-4 linear alkyl group or a hydrogen atom, and even more preferably R 1 to R 5 are each a methyl group or a hydrogen atom.

[0083] Other specific examples of the compound represented by formula (2) include those in which R 1 , R 2 , R 4 and R 5 are each a hydrogen atom and R 3 is a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group,

[0084] an alkylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group (preferably a hydrogen atom or an alkyl group, more preferably a hydrogen atom or a C 1-8 alkyl group, even more preferably a hydrogen atom or a C 1-4 alkyl group, and particularly preferably a methyl group).

[0085] In the diphenylurea structure of formula (2), the position of the substituent bonded to one benzene ring relative to the aminocarbonyl group on the benzene ring can be ortho, meta or para, preferably ortho or meta, and more preferably meta.

[0086] The compound represented by the formula (2) is not particularly limited, and is preferably at least one selected from the group consisting of 3-[(phenylcarbamoyl)amino]phenyl 4-methylbenzenesulfonate, 2-[(phenylcarbamoyl)amino]phenyl 4-methylbenzenesulfonate, and 4-[(phenylcarbamoyl)amino]phenyl 4-methylbenzenesulfonate. Among them, 3-[(phenylcarbamoyl)amino]phenyl 4-methylbenzenesulfonate is preferred.

[0087] The content of the compound represented by the formula (2) is not particularly limited, and can be adjusted according to the leuco dye used. Generally, the content of the compound represented by the formula (2) is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, even more preferably 1 part by mass or more, still more preferably 1.2 part by mass or more, and particularly preferably 1.5 part by mass or more, relative to 1 part by mass of the leuco dye. The content of the compound represented by the formula (2) is also preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less, relative to 1 part by mass of the leuco dye. Setting the content of the compound represented by the formula (2) to 0.5 part by mass or more can improve the recording performance. Setting the content of the compound represented by the formula (2) to 10 parts by mass or less can effectively reduce the background fogging in a high-temperature environment.

[0088] The content of the compound represented by the formula (3) is not particularly limited, and can be adjusted according to the leuco dye used. Generally, the content is preferably 0.5 part by mass or more, more preferably 0.8 part by mass or more, even more preferably 1 part by mass or more, still more preferably 1.2 part by mass or more, and particularly preferably 1.5 part by mass or more, relative to 1 part by mass of the leuco dye. The content of the compound represented by the formula (3) is also preferably 10 parts by mass or less, more preferably 5 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 3.5 parts by mass or less, relative to 1 part by mass of the leuco dye. Setting the content to 0.5 part by mass or more can improve the recording performance. Setting the content to 10 parts by mass or less can effectively reduce the background fogging in a high-temperature environment.

[0089] As long as the effects of the present invention are not impaired, a color former other than the N,N'-diarylurea compound represented by the above formula (1), the compound represented by the above formula (2), and the compound represented by the above formula (3) may also be included.

[0090] In the present invention, the thermosensitive recording layer may further contain a sensitizer. The use of the sensitizer enhances the recording sensitivity. Examples of available sensitizers include stearic acid amide, methoxycarbonyl-N-stearoyl benzamide, N-benzoyl stearic acid amide, N-eicosanoic acid amide, ethylene bis-stearic acid amide, behenic acid amide, methylene bis-stearic acid amide, N-hydroxymethyl stearic acid amide, dibenzyl terephthalate, dimethyl terephthalate, dioctyl terephthalate, diphenyl sulfone, benzyl p-benzyloxybenzoate, phenyl 1-hydroxy-2-naphthoate, 2-naphthyl benzyl ether, m-terphenyl, p-benzylbiphenyl, oxalic acid bis-p-chlorobenzyl ester, oxalic acid bis-p-methylbenzyl ester, oxalic acid dibenzyl ester, p-tolyl biphenyl ether, bis(p-methoxyphenoxyethyl) ether, 1,2-bis(3-methylphenoxy)ethane, 1,2-bis(4-methylphenoxy)ethane, 1,2-bis(4-methoxyphenoxy)ethane, 1,2-bis(4-chlorophenoxy)ethane, 1,2-diphenoxyethane, 1-(4-methoxyphenoxy)-2-(3-methylphenoxy)ethane, p-methylthiophenyl benzyl ether, 1,4-bis(phenylthio)butane, p-acetotoluidide, p-ethoxyacetoacetanilide, N-acetoacetyl-p-toluidide, 1,2-diphenoxytoluene, bis(β-biphenylethoxy)benzene, p-bis(vinyloxyethoxy)benzene, 1-isopropylphenyl-2-phenylethane, di-o-chlorobenzyl adipate, 1,2-bis(3,4-dimethylphenyl)ethane, 1,3-bis(2-naphthyloxy)propane, biphenyl, benzophenone, and the like. Among them, 1,2-bis(3-methylphenoxy)ethane is preferred. These sensitizers can be used in combination as long as the combined use does not impair the effects of the present invention. The content of the sensitizer may be an effective amount for sensitization, and is generally preferably 5 to 30% by mass, more preferably 10 to 30% by mass, and even more preferably 15 to 25% by mass based on the total solid content of the thermosensitive recording layer.

[0091] In the present invention, the thermosensitive recording layer may further contain a stabilizer, mainly for further enhancing the preservability of the developed image. As such stabilizers, for example, at least one selected from the group consisting of: phenolic compounds such as 1,1,3-tris(2-methyl-4-hydroxy-5-cyclohexylphenyl)butane, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 1,1-bis(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 4,4’-[1,4-phenylenebis(1-methylethylene)]bisphenol and 4,4’-[1,3-phenylenebis(1-methylethylene)]bisphenol; epoxy compounds such as 4-benzyloxyphenyl-4’-(2-methyl-2,3-epoxypropoxy)phenyl sulfone, 4-(2-methyl-1,2-epoxyethyl)diphenyl sulfone and 4-(2-ethyl-1,2-epoxyethyl)diphenyl sulfone; and isocyanuric acid compounds such as 1,3,5-tris(2,6-dimethylbenzyl-3-hydroxy-4-tert-butyl)isocyanuric acid can be used. Of course, the available stabilizers are not limited to these compounds, and two or more such compounds can be used in combination as needed.

[0092] When using a stabilizer, its usage amount can be an effective amount for improving the image preservability. The stabilizer is usually preferably used in an amount of about 1 to 25% by mass, and more preferably about 5 to 20% by mass, based on the total solid content of the thermosensitive recording layer.

[0093] As other components constituting the thermosensitive recording layer, inorganic or organic pigments, crosslinking agents, waxes, metal soaps, water resistance improvers, dispersants, colored dyes, fluorescent dyes and other auxiliaries can be used as needed.

[0094] Various inorganic pigments can be used as the inorganic pigment. Specific examples include inorganic pigments such as calcium carbonate, such as light calcium carbonate; aluminum hydroxide; clays such as kaolin; and talc. Among them, the inorganic pigment is preferably at least one selected from the group consisting of calcium carbonate, aluminum hydroxide and clay. The content of the inorganic pigment can be selected from a wide range, and based on the total solid content of the thermosensitive recording layer, it is preferably 2 to 40% by mass, more preferably 3 to 30% by mass, and even more preferably 4 to 20% by mass.

[0095] When the thermosensitive recording layer contains a crosslinking agent, the water resistance of the thermosensitive recording layer can be improved. Examples of the crosslinking agent include aldehyde compounds such as glyoxal; polyamine compounds such as polyethyleneimine; epoxy compounds, polyamide resins, melamine resins, glyoxylates, dimethylolurea compounds, aziridine compounds, blocked isocyanate compounds; inorganic compounds such as ammonium persulfate, iron chloride, magnesium chloride, sodium tetraborate, and potassium tetraborate; boric acid, boric acid triester, boron-based polymers, hydrazide compounds such as adipic dihydrazide, and glyoxylates, etc. These can be used alone or in combination of two or more. The amount of the crosslinking agent used is preferably about 0.2 to 5% by mass, and more preferably about 0.3 to 3% by mass based on the total solid content of the thermosensitive recording layer.

[0096] The thermosensitive recording layer is formed on a support as follows: for example, by using water as a dispersion medium and using at least one of various stirrers or wet pulverizers such as a ball mill, a co-ball mill, a grinder, or a vertical or horizontal sand mill, a leuco dye and a developer, and optionally, a sensitizer and a stabilizer, together or separately, are dispersed with a water-soluble synthetic polymer compound such as polyacrylamide, polyvinylpyrrolidone, polyvinyl alcohol, methyl cellulose, or a styrene-maleic anhydride copolymer salt, and other additives such as a surfactant to form a dispersion; then, the dispersion obtained by reducing the average particle size to 2 μm or less is mixed with a binder and optionally an auxiliary agent, etc. to prepare a coating composition for the thermosensitive recording layer; the coating composition for the thermosensitive recording layer is coated on the support; and then dried. The coating amount of the thermosensitive recording layer is not particularly limited, and in terms of dry mass, it is preferably about 1 to 12 g / m 2 , more preferably 2 to 10 g / m 2 , even more preferably 2.5 to 8 g / m 2 , and particularly preferably 3 to 5.5 g / m 2 . Note that, if necessary, the thermosensitive recording layer can be formed into two or more separate layers, and the composition and coating amount of each layer can be the same or different.

[0097] Protective layer

[0098] If necessary, the thermosensitive recording body can include a protective layer formed on the thermosensitive recording layer. The protective layer preferably contains a pigment and a binder. The protective layer preferably further contains a lubricant such as polyolefin wax or zinc stearate to prevent the protective layer from adhering to the thermal head. The protective layer can also contain an ultraviolet absorber. When a glossy protective layer is formed, the obtained product can have increased added value.

[0099] The pigment contained in the protective layer is not particularly limited. Examples include inorganic pigments such as amorphous silica, kaolin, clay, light calcium carbonate, heavy calcium carbonate, calcined kaolin, titanium oxide, magnesium carbonate, aluminum hydroxide, colloidal silica, and synthetic layered mica; and plastic pigments such as urea-formalin resin fillers; etc.

[0100] The binder contained in the protective layer is not particularly limited, and an aqueous binder selected from a water-soluble binder and a water-dispersible binder can be used. The binder can be appropriately selected from binders that can be used for the thermosensitive recording layer. Among them, various modified polyvinyl alcohols, such as acetoacetyl modified polyvinyl alcohol, carboxyl modified polyvinyl alcohol and diacetone modified polyvinyl alcohol, can be more preferably used. From the viewpoint of improving water barrier resistance, acetoacetyl modified polyvinyl alcohol is more preferably used.

[0101] For example, a protective layer coating is prepared by mixing a pigment and a binder with an auxiliary agent or the like using water as a dispersion medium, applying the coating to the thermosensitive recording layer, and then drying to form a protective layer on the thermosensitive recording layer. The coating amount of the protective layer coating is not particularly limited, and is preferably about 0.3 to 15 g / m 2 in terms of dry mass. 2 , more preferably about 0.3 to 10 g / m 2 , even more preferably about 0.5 to 8 g / m 2 , particularly preferably about 1 to 8 g / m 2 , and more preferably about 1 to 5 g / m 2 The protective layer may be formed as two or more separate layers as necessary, and the composition and coating amount of each layer may be the same or different.

[0102] Other layers

[0103] In the present invention, the thermosensitive recording body preferably has an adhesive layer on at least one surface of the support. This can increase the added value of the thermosensitive recording body. For example, adhesive paper, rewet adhesive paper or delayed adhesive paper can be formed as an adhesive layer by coating one surface of the support with, for example, an adhesive, a rewet adhesive or a delayed adhesive type adhesive. Recording paper capable of double-sided recording can also be formed by giving the surface of the support opposite to the thermosensitive recording layer as a function of thermal transfer paper, inkjet recording paper, carbonless paper, electrostatic recording paper or electrostatic copy paper. Of course, the thermosensitive recording body can be formed as a double-sided thermosensitive recording body. A back layer can also be provided to suppress the penetration of oil and plasticizer from the back of the thermosensitive recording body, or for curl control and antistatic purposes. The thermosensitive recording body can also be formed as a linerless label that does not require a release paper by forming a release layer containing silicone on a protective layer and applying an adhesive to one side.

[0104] Thermosensitive recording body

[0105] The thermosensitive recording body can be produced by forming the above-mentioned respective layers on a support. Any known coating method, such as the air knife method, doctor blade method, gravure method, roll coating method, spraying method, dipping method, bar coating method, curtain coating method, slot die method, slide die method, and extrusion method, can be used as the method for forming the above-mentioned respective layers on the support. Each coating material can be coated in such a manner that the first coating material is coated and dried, and then the second coating material is coated and dried to form layer upon layer, or the same coating material can be coated alone to form two or more layers. In addition, simultaneous multi-layer coating can also be carried out, in which all the coating materials are coated at once to simultaneously form two or more layers. After forming each layer or at any stage after forming all the layers, the layer can be smoothed by a known method such as over-calendaring or soft-calendaring.

[0106] Examples

[0107] The present invention will be described in more detail with reference to the examples. However, the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass". The average particle size was measured using a SALD2200 laser diffraction particle size distribution analyzer (manufactured by Shimadzu Corporation). The "average particle size" used herein refers to the median diameter (D50).

[0108] Example 1

[0109] (1) Preparation of leuco dye dispersion (Dispersion A)

[0110] 40 parts of 3-di(n-butyl)amino-6-methyl-7-anilinofluoran, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water were mixed. The resulting mixture was pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinder) to an average particle size of 0.5 μm, thereby obtaining a leuco dye dispersion (Dispersion A).

[0111] (2) Preparation of developer dispersion (Dispersion B)

[0112] 40 parts of N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water were mixed. The resulting mixture was pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm, thereby obtaining a developer dispersion (Dispersion B).

[0113] (3) Preparation of sensitizer dispersion (Dispersion C)

[0114] Forty parts of 1,2-bis(3-methylphenoxy)ethane (trade name: KS-232, manufactured by Sankosha Co., Ltd.), forty parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and twenty parts of water were mixed. The resulting mixture was pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinding machine) to an average particle size of 1.0 μm, thereby obtaining a sensitizer dispersion (dispersion C).

[0115] (4) Preparation of the coating composition for the thermosensitive recording layer

[0116] Thirty-four point one parts of dispersion A, sixty-eight point two parts of dispersion B, forty-five point five parts of dispersion C, twenty-six parts of an olefin-acrylic copolymer salt (trade name: Hi-Tec S-3121, aqueous dispersion of ethylene-acrylic copolymer ammonium salt, manufactured by Toho Chemical Industry Co., Ltd., solid content: 26.5%), forty-one point seven parts of a styrene-butadiene latex (trade name: Smartex PA-9281, manufactured by Nippon A&L Co., Ltd., solid content concentration: 48%), five parts of calcium carbonate (trade name: Brilliant 15, manufactured by Shiraishi Kogyo Co., Ltd.), zero point five parts of adipic dihydrazide (manufactured by Otsuka Chemical Co., Ltd.), and two hundred parts of water were mixed and stirred, thereby obtaining the coating composition for the thermosensitive recording layer.

[0117] (5) Preparation of the coating composition for the protective layer

[0118] A composition containing 208 parts of a 12% aqueous solution of acetoacetylated polyvinyl alcohol (trade name: Gohsenx Z-200, manufactured by The Nippon Synthetic Chemical Industry Co., Ltd.), 55 parts of kaolin (trade name: Hydragloss 90, manufactured by KaMin LLC), 2.5 parts of polyethylene wax (trade name: Chemipearl W-400, manufactured by Mitsui Chemicals Inc.; solid content concentration: 40%), 20.8 parts of zinc stearate (trade name: Hidorin Z-8-36, manufactured by Chukyo Yushi Co., Ltd.; solid content concentration: 36%), and 150 parts of water was mixed and stirred, thereby obtaining the coating composition for the protective layer.

[0119] (6) Preparation of the thermosensitive recording medium

[0120] Using synthetic paper (trade name: YUPO FPG95, paper thickness: 95 μm, manufactured by Yupo Corporation), the synthetic paper is produced by kneading a polyolefin resin and calcium carbonate as a white inorganic pigment by heating, extruding the kneaded product through a die, stretching the extruded product in the longitudinal direction, laminating films made of a polyolefin resin and calcium carbonate as a white inorganic pigment on both sides of the stretched product, and then stretching the resulting product in the transverse direction to make it opaque. A thermosensitive recording layer is coated on one side of the synthetic paper with a coating solution and dried so that the dry mass is 4.0 g / m 2 to form a thermosensitive recording layer, and a protective layer is coated on it with a coating solution and dried so that the dry mass is 2.5 g / m 2 to form a protective layer. Then, the surface is smoothed with a supercalender to obtain a thermosensitive recording medium.

[0121] Example 2

[0122] (7) Preparation of a developer dispersion (Dispersion D)

[0123] 40 parts of 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate, 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water are mixed. The resulting mixture is pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm to obtain a developer dispersion (Dispersion D).

[0124] A thermosensitive recording medium is obtained in the same manner as in Example 1, except that Dispersion D is used instead of Dispersion B in the preparation of the coating solution for the thermosensitive recording layer in Example 1.

[0125] Example 3

[0126] (8) Preparation of a developer dispersion (Dispersion E)

[0127] 40 parts of the compound represented by formula (3), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water are mixed. The resulting mixture is pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm to obtain a developer dispersion (Dispersion E).

[0128] A thermosensitive recording medium is obtained in the same manner as in Example 1, except that Dispersion E is used instead of Dispersion B in the preparation of the coating solution for the thermosensitive recording layer in Example 1.

[0129] Comparative Example 1

[0130] (9) Preparation of Color Developer Dispersion (Dispersion F)

[0131] Mix 40 parts of N-p-toluenesulfonyl-N'-3-(p-toluenesulfonyloxy)phenylurea (trade name: PF-201, produced by Solenis), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water. Grind the resulting mixture with a sand mill (produced by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm to obtain a color developer dispersion (dispersion F).

[0132] (10) Preparation of Color Developer Dispersion (Dispersion G)

[0133] Mix 40 parts of 4,4'-bis[(4-methyl-3-phenoxycarbonylaminophenyl)ureido]diphenyl sulfone (trade name: UU, produced by Chemipro Kasei Kaisha, Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water. Grind the resulting mixture with a sand mill (produced by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm to obtain a color developer dispersion (dispersion G).

[0134] A thermal recording medium was obtained in the same manner as in Example 1, except that in the preparation of the coating composition for the thermal recording layer in Example 1, 56.8 parts of dispersion F and 11.4 parts of dispersion G were used instead of 68.2 parts of dispersion B.

[0135] Comparative Example 2

[0136] (11) Preparation of Color Developer Dispersion (Dispersion H)

[0137] Mix 40 parts of 4-allyloxy-4'-hydroxydiphenyl sulfone (trade name: BPS-MAE, produced by Nicca Chemical Co., Ltd.), 40 parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and 20 parts of water. Grind the resulting mixture with a sand mill (produced by Aimex Co., Ltd., sand grinder) to an average particle size of 1.0 μm to obtain a color developer dispersion (dispersion H).

[0138] (12) Preparation of Color Developer Dispersion (Dispersion I)

[0139] Forty parts of a crosslinked diphenylsulfone compound represented by the following formula (4) (trade name: D-90, manufactured by Nippon Soda Co., Ltd.), forty parts of a 10% aqueous solution of polyvinyl alcohol (degree of polymerization: 500, saponification degree: 88%), and twenty parts of water were mixed. The resulting mixture was pulverized with a sand mill (manufactured by Aimex Co., Ltd., sand grinder) to an average particle diameter of 1.0 μm, thereby obtaining a developer dispersion (dispersion I).

[0140]

[0141] Wherein n represents an integer from 1 to 6.

[0142] A thermosensitive recording body was obtained in the same manner as in Example 1, except that in the preparation of the coating for the thermosensitive recording layer in Example 1, 56.8 parts of dispersion H and 11.4 parts of dispersion I were used instead of 68.2 parts of dispersion B.

[0143] The thermosensitive recording body thus obtained was evaluated as follows. Table 1 shows the results.

[0144] Recording density

[0145] Using a thermosensitive recording evaluator (trade name: TH-PMD, manufactured by Ohkura Electric Co., Ltd.), an image was recorded on each thermosensitive recording body with an applied energy of 0.25 mJ / dot to obtain the highest color development density. The reflection density of the obtained recording portion was measured using a spectrophotometric densitometer (X-Rite 504, manufactured by X-Rite). The evaluation criteria for the recording density are as follows.

[0146] Density of 1.30 or more: The printed content is clear and excellent.

[0147] Density of 1.10 or more and less than 1.30: The readability of the barcode is good and there is no problem in actual use.

[0148] Density less than 1.10: The readability of the barcode is slightly poor and there is a problem in actual use.

[0149] Heat resistance at 100 °C

[0150] Using a thermosensitive recording evaluator (trade name: TH-PMD, manufactured by Ohkura Electric Co., Ltd.), an image was recorded on each thermosensitive recording body with an applied energy of 0.25 mJ / dot (maximum color development density).

[0151] Cut each of the obtained paper sheets into a length of 9 cm and a width of 4 cm. Perform a treatment on the obtained paper sheets in which the paper sheets are left standing in a dryer at 100 °C for 1 hour. Measure the reflection density of the background part (unprinted blank part) before and after the treatment, and the reflection density of the recording part after the treatment, using a spectrophotometer (X-Rite 504, manufactured by X-Rite). The evaluation criteria for the background part are as follows. The evaluation criteria for the recording part are based on the above evaluation criteria for the recording density.

[0152] When the background part density is 0.10 or less: The heat resistance is excellent.

[0153] When the background part density is less than 0.20 but greater than 0.10: There is no problem in actual use.

[0154] When the background part density exceeds 0.20: The background fogging is significant and the heat resistance is poor.

[0155] Transfer printing test

[0156] Using a thermal recording evaluation machine (trade name: TH-PMD, manufactured by Ohkura Electric Co., Ltd.), record an image on each thermal recording medium with an applied energy of 0.25 mJ / dot (maximum color development density). Cut each of the obtained paper sheets into a length of 9 cm and a width of 4 cm to prepare two identical paper sheets. Spray water onto the printing surface side of each paper sheet, and then overlap the two paper sheets with their printing surfaces facing each other. Place a 1 kg weight on the overlapped test pieces, and leave the test pieces and the weight standing in an environment of 23 °C and 65% RH for 3 days. After leaving them standing for 3 days, leave the test pieces and the weight standing in a dryer at 40 °C for 1 day to evaporate the moisture. After the moisture has evaporated, peel the two test pieces from each other and visually observe whether the printed content of one test piece has been transferred to the printing surface of the other test piece. The evaluation criteria for the transfer of the printed content are as follows.

[0157] A: When visually observed, there is no transfer of the printed content at all.

[0158] B: Transfer of the printed content is visually observed.

[0159] Table 1

[0160]

[0161] Industrial applicability

[0162] The thermal recording medium of the present invention has no risk of transferring the printed content to the printing surface and has excellent heat-resistant background fogging properties, and thus fully meets the requirements for performance improvement in applications such as handheld terminals and delivery slips that require water barrier resistance and are used in harsh environments.

Claims

1. A heat-sensitive recording body, which comprises a heat-sensitive recording layer on a support The heat-sensitive recording layer contains a leuco dye, a developer and a binder The heat-sensitive recording layer contains an olefin-acrylic copolymer salt and a styrene-butadiene latex as the binder, and contains at least one non-phenolic developer selected from the group consisting of N,N'-diarylurea compounds represented by the following formula (1), compounds represented by the following formula (2) and compounds represented by the following formula (3) as the developer: wherein R represents C 1-12 alkyl, C 7-12 aralkyl or C 6-12 aryl, and the aralkyl and aryl may be substituted by C 1-12 alkyl, C 1-12 alkoxy, C 6-12 aryl or a halogen atom, and a plurality of Rs may be the same or different, and A 1 represents a hydrogen atom or a C 1-4 alkyl group, and a plurality of A 1 may be the same or different; wherein R 1 to R 5 are the same or different and each represents a hydrogen atom, a halogen atom, a nitro group, an amino group, an alkyl group, an alkoxy group, an aryloxy group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylsulfonylamino group, an arylsulfonylamino group, a monoalkylamino group, a dialkylamino group or an arylamino group; 。 2. The heat-sensitive recording body according to claim 1, wherein the N,N'-diarylurea compound represented by the formula (1) is at least one selected from the group consisting of: N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(o-toluenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(mesitylenesulfonyloxy)phenyl]urea, N,N'-di-[3-(4-ethylbenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(2-naphthalenesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-methoxybenzenesulfonyloxy)phenyl]urea, N,N'-di-[3-(benzylsulfonyloxy)phenyl]urea, N,N'-di-[3-(ethanesulfonyloxy)phenyl]urea, N,N'-di-[3-(p-toluenesulfonyloxy)-4-methyl-phenyl]urea, N,N'-di-[4-(p-toluenesulfonyloxy)phenyl]urea, N,N'-di-[4-(benzenesulfonyloxy)phenyl]urea, N,N'-di-[4-(ethanesulfonyloxy)phenyl]urea and N,N'-di-[2-(p-toluenesulfonyloxy)]phenylurea.

3. The heat-sensitive recording body according to claim 1, wherein the N,N'-diarylurea compound represented by the formula (1) is N,N'-di-[3-(p-toluenesulfonyloxy)phenyl]urea.

4. The heat-sensitive recording body according to claim 1, wherein the compound represented by the formula (2) is 3-[(phenylcarbamoyl)amino]phenyl-4-methylbenzenesulfonate.

5. The heat-sensitive recording body according to claim 1, wherein based on the total solid content of the heat-sensitive recording layer, the content of the olefin-acrylic copolymer salt is 4 to 25% by mass, and the content of the styrene-butadiene latex is 15 to 40% by mass.

6. The heat-sensitive recording body according to claim 1, wherein the content of the olefin-acrylic copolymer salt is 10 to 150 parts by mass relative to 100 parts by mass of the styrene-butadiene latex.

7. The heat-sensitive recording body according to claim 1, wherein based on the total solid content of the heat-sensitive recording layer, the total content of the olefin-acrylic copolymer salt and the styrene-butadiene latex is 25 to 50% by mass.

8. The heat-sensitive recording body according to claim 1, wherein the support is synthetic paper or a synthetic resin film.

9. The heat-sensitive recording body according to claim 1, wherein the support contains a polyolefin resin.

10. The thermosensitive recording body according to claim 1, which includes a protective layer on the thermosensitive recording layer, and the protective layer contains acetoacetylated polyvinyl alcohol as a binder.

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